Conventionally, various packaging materials have been developed and proposed for filling and packaging of a variety of articles including foods and beverages, drugs, cosmetics, detergents, chemicals and the like. The most important issue for such packaging materials is to have gas barrier properties against oxygen gas, water vapor and the like. Another issue, particularly for packaging materials for contents that progressively undergo decomposition and deterioration of their components by light, is a requirement for a light-shielding property to shield them from penetration of exterior light. Among such packaging materials in the prior art there have been used three-layer structure laminates, that are obtained by laminating a printed transparent plastic film, an aluminum vapor deposition film or aluminum foil having a gas barrier property and a light-shielding property, and a sealant film (PTL 1).
However, packaging materials made of such three-layer structure laminates, because of their multilayer structures, use large amounts of materials and have thick bulk, leading to problems in terms of production cost, transport cost and the like. In addition, a laminate using an aluminum foil introduces problems such as poor environment stability, and a laminate using an aluminum vapor deposition film has problems of poor gas barrier properties or light-shielding properties, and decomposition or deterioration of contents.
Furthermore, when the contents are powders or granules such as salt, sugar, powdered soup, powdered milk, instant coffee, furikake, powdered or granulated seasonings, powdered detergents or the like, for example, a very high water vapor-barrier property is required in order to maintain the powdered or granular nature of the contents, but conventional packaging materials cannot satisfy this requirement, and quality has been impaired due to moisture absorption by the contents.